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Most of us are getting the shivers only mentioning the RDP. No worries guys, in this section of our PADI IDC and Divemaster Classroom, I will explain to you with links to physiology why it is so important to know how that little card works in an computer assisted age.
We will start off by talking about where the RDP comes from and explaining what principle it works on.
Before the world figured out how decompression works on humans, mister John Haldean demonstrated DCS „the bends“ in goats which was a success as it proved he was right with his theory. After those trials, he started to experiment with volunteers of the royal navy. As a result of that the first decompression tables were born.
In 1988 Dr. Raymond Rogers applied Haldaneans concept to recreational diving which is, as we know, more conservative. Even today most of the tables and computer algorithms are based on the work of Haldanean.
Before RDP tables where implemented, early sport divers used Navy tables with a 120 minute compartment wash out. Our RDP table based the surface interval credit on the 60 minute compartment. This means basically that the RDP table states you are getting rid of nitrogen 50% faster then the Navy tables are.
Navy divers were doing decompression dives and in general, one single dive. As recreational divers we want to do repetitive dives and shorter surface intervals. This theory gave us limited depth but therefore multiple dives and shorter surface intervals using the RDP.
A compartment is a tissue group, one of 14 tissue compartments used in the RDP table. We have hard tissues in our body like bones which will fill up with Nitrogen slower than muscles or blood vessels do. On the navy tables therefore they believed that it takes 120 min for the slowest of 6 compartment tissues to be equally washed out from nitrogen. The RDP table uses faster „gas wash out“ tissue compartments.
All letters on the RDP table are designated to those 14 different tissue compartments in your body, and cannot be interchanged with any other tables except the Recreational dive Planer.
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